PS: The water feature is even down for matinee. http://www.refinery29.com/2016/02/102431/new-york-niagara-fa...
But isn't that what it does? Unless you start to limit (more than before) the waterflow to the falls themselves, which probably would meet resistance from conservationists.
(I understand the Lewiston power plant already does have capability to pump water up.)
And, many places don't have such reservoir capacity at hand. Over here any new reservoir project meets fierece resistance, and it's rather the other way round: nature conservationists want to shut down existing hydroelectric capacity.
It's complex there are few environmental effects from blocking the falls as they are already one way and tend to kill fish that make the trip. However, there is a treaty that set's minimum flow levels and more water is diverted at night to a holding area which is then used for hydro in the day.
https://en.wikipedia.org/wiki/Niagara_Falls_hydroelectric_ge...
Anyway, the area already has plenty of pumped storage it's only by importing a lot of power that you would need to expand. But, at that point you can scale really far with few environmental costs.
Or in the extreme case, consider Lake Erie is next to Lake Ontario. Pumping extra water back up for a few hours a day would have minimal issues as boat bilge water has already cross contaminated them.